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<script>
    const target = {
    field1: 1,
    field2: undefined,
    field3: {
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    },
    field4: [2, 4, 8]
    }
    target.target = target;
    function clone(target, map = new Map()) {
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            cloneTarget[key] = clone(target[key], map);
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        return cloneTarget;
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        return target;
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console.log(clone(target))
</script> 
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